The analysis of biological specimens from melanoma swine has been completed. Plasma and tissue samples from animals with and without tumor burden were analyzed for biogenic amines, norepinephrine (NE), dopamine (DA), serotonin (5-HT) and tyramine (TYM); sialic acid (N-acetylneuraminic acid); free amino acids and ninhydrin-positive compounds (29 compounds). We found that DA levels in plasma were significantly lower in animals with melanoma lesions as compared with normal animals. NE levels were slightly increased in plasma of swine with melanocytic lesions. Serotonin was at trace amount levels and TYM showed elevated amounts for two pigs with tumor. The biogenic amine levels in normal tissue from pigs with and without melanocytic lesions were not significantly different; however, in melanoma lesions the levels for NE, DA, 5-HT and TYM were significantly elevated. We found significantly higher levels of sialic acid in serum of most pigs one week after birth, decreasing thereafter in normal pigs while generally remaining elevated or even increasing in animals with melanoma lesions. A total of 29 different compounds (free amino acids and ninhydrin-positive compounds) were assayed by classical ion exchange. We found lower levels of proline, serine, tyrosine and hydroxyproline in plasma from tumor-bearing swine as compared with normal swine. During our studies, chromatographic methods have been advanced and modified and two publications resulted from our research on biogenic amines by HPLC. The significant changes observed during the exploratory study warranted another study using a larger swine population and longer life span with tumor burden, without tumor and with spontaneous regression of melanoma. Two of the pigs with tumor burden have shown complete regression of all lesions. The larger numbers of the unique animal model being studied over a longer life span will provide more information on how biochemical changes are related to the course of melanoma.